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1999 ford e350 overheating

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New User

Feb 7, 2021, 11:07 AM

Post #1 of 4 (420 views)
1999 ford e350 overheating Sign In

I have a 1999 ford e350 with a 6.8 L V10 that has a problem overheating when going up mountain roads. I have already replaced the cylinder head temperature sensor and the thermostat to try to fix it, but it did not. I had the coolant system flushed a few months ago because there was oil in the coolant from a bad oil cooler. This was done before the overheating problem started. The fan seems to be working right to my untrained eyes though. What would be the next thing you'd check. I have seen that an air bubble in the coolant system could do something like this or maybe I need a new radiator or something. The car has coolant and runs fine otherwise, just not up steep long roads. The car has almost 200,000 miles on it.

Hammer Time
Ultimate Carjunky / Moderator
Hammer Time profile image

Feb 7, 2021, 11:52 AM

Post #2 of 4 (412 views)
Re: 1999 ford e350 overheating Sign In

You're talking about circumstances that would strain even the best cooling system.

If you previously had oil in the coolant then you likely have sludge restrictions in the radiator now. Having 200K isn't working in your favor either.
About the only way you are going to resolve this situation is to increase the cooling capacity and about the only way to do that is with a larger radiator.


We offer help in answering questions, clarifying things or giving advice but we are not a substitute for an on-site inspection by a professional.

Tom Greenleaf
Ultimate Carjunky / Moderator
Tom Greenleaf profile image

Feb 7, 2021, 11:59 AM

Post #3 of 4 (410 views)
Re: 1999 ford e350 overheating Sign In

Some questions for you: What type of oil, engine oil or ATF for trans? Where is this oil cooler? Inside radiator or both that and a separate one also with oil cooler in radiator?
You may have both engine and trans ATF oil coolers for this thing need to know how they are cooled. Either using the radiator the radiator has to go or it's not fixed it putting more in making a foamy mess that doesn't exchange heat plus an oil in coolant is ruining rubber parts. AFTER that's fixed it's hard to flush out that oil really need soap/water and lots of it till clear then fill the items properly again with new respectively.
It isn't going to flush right out and keep going it's adding more is my guess.

Is fan belt driven or both a belt driven one and electric fan(s) if so are those throwing off heat when on - you can feel the warm air coming off of them. Heater should be strong as ever if dual both putting out strong heat upon request any rubber hoses are probably soft now not compatible with an oil, nor is water pump's seal or radiator pressure cap.

The Vans loaded up with coolers some optional for severe use IDK what set up this would have all or some of what was mentioned.
Yes it will need a new radiator if cooler is in an end tank. If not blowing heat for heaters either clogged up or never got air out or some of both.
Just how much does it overheat? Boiling over, puking out on ground or just not holding steady for you? It matters if overheating it opens the book on what possible engine damage has already been done!

Also need to know if coolant got into oil not just an oil into coolant if so this is a much more serious problem for transmission and lucky if it didn't already harm engine.
I suggest you stop and really know what oils are cooled how and where in this and determine damage already so you know better costs to continue on with this cost wish could be really shocking plus the whole thing has 200K on it, just might have had it cost wise for a new longer life when fixed?


New User

Feb 8, 2021, 3:45 PM

Post #4 of 4 (372 views)
Re: 1999 ford e350 overheating Sign In

Okay thank you so much

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